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YOUR RESEARCHOil Pressure Question
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Reported cause · Original poster
I'm holding off on any other work to the car until the pressure issue is taken care of - so I'll keep this updated.
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Suggestion
Unfortunately id'ing a squirter problem, or excessive clearances, or an internal oil leak is not easy without taking the engine apart and checking clearances and then ensuring during reassembly all oil passages/galleys and holes are properly sealed.
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Performed · outcome unconfirmed · Original poster
New spring installed and the oil was changed over to 5W Motul.
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Performed · outcome unconfirmed
I have run both 0w-40 and 5w-50 (not a typo for 15w-50) in both of my cars and I can't tell which oil is in the engine by the Turbo's oil pressure gage or by any other method other than looking at the label of the bottles of oil I used or what the tech wrote on the paperwork.
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More than likely the gauge measure the voltage drop from the pin to ground controls the gauge off of that.
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Check clearances
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Suggestion
Unfortunately id'ing a squirter problem, or excessive clearances, or an internal oil leak is not easy without taking the engine apart and checking clearances and then ensuring during reassembly all oil passages/galleys and holes are properly sealed.
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Suggestion
You can also check the oil pressure relief Spring , it's easy to get at, it's accessible underneath the engine on the bottom of the oil pump without removing anything else , it's the single quite large hex bolt on the bottom of the oil pump, the spring inside can snap giving low oil pressure, obviously oil will come out when you remove it unless you do the oil change at the same time, also there is an updated Spring used on later cars which is slightly longer and can bring pressure up if you don't already have this!
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Suggestion
If the oil pump is "easy" to replace and this replaces just more than the gears but also the housing in which the gears run, it might be worth throwing a new pump at the low oil pressure problem.
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Suggestion
Could be wear on the main pump , depends what this engine got on it's build, new bearings, oil squirters can be a problem , wear on the cam bearings which can't be changed, lifters and lifter housing , not sure on the millers maybe an equivalent weight oil with a good wear package rated for high performance cars??
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Diagnosing an issue now... . 99 996 3.4 70K miles
Cold Start - oil pressure indicates 3.75 - 4.5.
Oil level good.
Not sure what oil is in it now.
After warmup - occasional pressure light when backing into the garage (I'm learning the clutch on this versus the 997).
Yesterday -
100 outside... Wasn't really pushing the car. 30 minute drive. Pressure starts fine then drops as the drive continues. Idle pressure (at lights) drops to .5 bar. As the ride continues - pressure light comes on at lights. Pressure will not climb over 2.5 bar at any RPM.
The way home (after 1 hour cooling off) was the same temp outside. No pressure lights came on, still .5 bar at idle - and consistent 2 bar at 3K RPM.
I have an oil pump piston and piston spring on order. I'm also going to change the oil to 5W40 (Motul) so I have a base line.
Step after that is a new sender.... maybe a trip to the indie to get a real read on the pressure?
Thoughts?
Stock gauge is unreliable ,so yes get the pressure mesured by a competent Indie. Agreed replace the piston and spring regardless.The smart guys use JGDT40 oil + a spin on filter.
Agree with m3driver...the sending unit is the place to start...but don't assume it might be that until you know for sure. If the sending unit is changed and you are getting the same readings, have the oil pressure checked with a mechanical guage by a qualified shop. Don't try to raise your pressure by adding thicker oil. Also, if you haven't changed your oil recently, do so now and check the filer and the sump for any metal.
I would also agree with the previous 2 posters. This silly little sending unit, when on it's way out, can give you all kinds of misinformation. First indication with mine was oil pressure dropping to zero! After a change of clothes and some investigation it was
this sender.
All good advice. New Sender for peace of mind. New (correct) oil and filter so thats a known quantity. Also think about cleaning the oil pick up pipe in the oil pan. It has a coarse mesh on it that could collect large debris and obstruct that path. No saying what that could possibly be...excess sealant from a previous oil pan opening or debris from the plastic timing chain guide, but it only costs you time, $10 dollars worth of new sump pan bolts, and a tube of sealant for further peace of mind.
Provided the re-seal of the oil sump plate doesn't result in any excess sealant applied replacing the sealant that the cleaning removed.
The sealant will make it through the mesh and be pulverized in the oil pump. This gets collected in the oil filter housing and is of course removed from the engine when the oil is changed.
The first oil change probably had some of this sealant trash in the oil filter housing oil and oil filter element.
If the oil pick up mesh was seriously blocked the engine would have expired by now.
+1 on changing the oil pressure sender first. I had a similar problem and a new sender corrected it. Changing to 5W40 wouldn't help - the 5 is the cold start oil viscosity; the 40 is the running temp viscosity. Your problem is when the engine is hot.
You can also check the oil pressure relief Spring , it's easy to get at, it's accessible underneath the engine on the bottom of the oil pump without removing anything else , it's the single quite large hex bolt on the bottom of the oil pump, the spring inside can snap giving low oil pressure, obviously oil will come out when you remove it unless you do the oil change at the same time, also there is an updated Spring used on later cars which is slightly longer and can bring pressure up if you don't already have this!
FYI. the sender is actually two senders in one unit. the first one gives you a variable reading for the gauge, and the other is fixed for the oil pressure light and the computer.
Who knows...I've seen some pictures of god awful jobs (post-factory) done with way too much sealant. And then theres the old aluminum foil top from the oil container down the filler, a perennial favorite! I guess I'm paranoid about oil pressure.
Any more info on how that works? I always assumed this was a simple analog sensor since it has only 2 primitive terminals. Didn't think about it much when I replaced mine, I guess it could be a CAN bus connection.
After removal of the stock unit there is a stamping on the hex nut of the pressures that each output measures. it says 0.3 +/- 0.15 bar, and says 0-5 bar for the other one. basically you have an on/off for the 0.3 +/- 0.15 bar that goes to the light and the computer for the dash screen, and then you have the other post that feeds the gauge. It is two pressure sensors in a single housing. Also, they are slightly different sizes so that you cant hook it up wrong. I dont think it is on the CAN bus, but i could be wrong about that, from what I could tell it is an analog output for the gauge, and a on off switch for the lights/computers screen. More than likely the gauge measure the voltage drop from the pin to ground controls the gauge off of that. the light/computer screen is looking for healthy voltage while above 0.3 bar +/- 0.15 bar. when the oil pressure gets too low the voltage crosses a threshold and pops the light and the computer screen.
100% accurate. Not on the CAN bus for sure. I don't think it's on the K-line either because its reading is not available on Durametric. However, that could be because it was not implemented by Porsche or it's implemented by Porsche but not by Durametric.
Makes total sense, 2 separate analog voltages and a chassis ground. (In retrospect I should have known it couldn't be CAN as there would need to be at least a 4th power terminal). Thx
Waiting on parts to come in - namely going to start with the spring and the piston. Indy verified low pressure with a pressure gauge.
If the spring doesn't do the trick - then I think the next step is to look at the oil pump.
I'm holding off on any other work to the car until the pressure issue is taken care of - so I'll keep this updated.
Drop the sump and check that pick-up tube... If the pressure is that low, it's probably more than the piston/spring...if that screen is blocked (i.e. no oil ) the pump can't make pressure.
New spring installed and the oil was changed over to 5W Motul.
There was a 1bar increase - idle is still around (just under) 1bar - 5K rpm is only 4.5 (just a bit less). So it's still out of spec. This is verified with a pressure gauge.
There was metal and plastic fragments found in the oil. The metal - and the amount of - wasn't found to be alarming by my indy (considering the motor was just rebuilt). The plastic though - not sure on that one unless there is an oil pump issue. The oil pick up tube wasn't blocked at all as was verified by my indy after installing the FVD deep sump / X51 pan.
Next step in my mind is the oil pump unless anyone has any other ideas.
You have established there is no problem with oil flow to the oil pump. Logically the next part in the oil route is the pump as you suggest. Of all the many M96 problems, worn pumps seem a low probability . A broken oil pump drive shaft is mentioned .Damage to the pump by FOM would be possible.
Time to study the oil flow diagrams
? Attach a diagram to your next post to keep everyone on the same page ? Are you loosing pressure from worn bearings ? If they are worn enough to cause pressure loss ,they may knock a little? If the bearing shells are wearing rapidly, there will be glittery debris in the sump. You said there is none?
2 links here:
http://www.renntech.org/forums/topic.../?_fromLogin=1
It is a bit tricky to understand it perfectly. Look how far away the pressure sensor is from the pump. Between the pump and the sensor ,all kinds of problems could be lurking?
And if the scavenge pumps are failing ,there will be very little oil returned to the sump - but you have a deep sump - so that worry is probably eliminated.
The diagram is actually Pedro's
http://www.pedrosgarage.com/Site_2/TechnoFix_DOF.html
There is a photo of the pump in this tear-down page - about 3/4 of the way down
http://www.rennsportkc.com/anatomy-o...t-kansas-city/
You could try millers nanodrive 10w 50 oil, it has a slightly thicker weight when hot so helps with hot idle and running pressures, is that motul 5w40, I was running castrol 5w 40 in mine and getting 1 bar hot idle now I get 1.5 with the millers , might do the job for you, it's the oil Barry at Hartech has developed with millers and recommends for these engines and he knows what he's talking about more than any of us lot do!!
Millers is a U.K. brand. Who sells it in USA ?
problem is the pump(s0?
http://www.rennsportkc.com/anatomy-o...t-kansas-city/
go 3/4 of the way down the page for a big color photo of the oil pump
Hi Schnell
Yes I know what the oil pump looks like since I've completely stripped and rebuilt my engine!
I'm not sure about the scavenge pumps, if they weren't doing their job and the oil was staying in the heads I would say intermittent starvation would be more likely as there would be no oil left in the sump for the main pump to collect .
Could be wear on the main pump , depends what this engine got on it's build, new bearings, oil squirters can be a problem , wear on the cam bearings which can't be changed, lifters and lifter housing , not sure on the millers maybe an equivalent weight oil with a good wear package rated for high performance cars??
I worry about using thicker oil as a band aid for a broader issue. Still wondering what the plastic is in the oil.
More info - the oil that came out was called "break in" oil - though never identified as to what it actually was. Further - it has been in the engine (from what I can tell) for less than 100 miles).
Either way - its out an Motul 5W40 is in now and the pressure still cannot get to spec of 5bar at 5K rpm.
Did you use a real pressure gage? One you can trust? And does it report gauge pressure or absolute pressure? Gauge pressure is zero-referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure.
If the oil pressure is indeed low then there can be an internal problem.
Generally an oil pump is not the problem. I was always told to when an engine was apart to just replace the oil pump on general principles. But one wants to be sure the new pump has the proper end clearances.
But an oil pump can't be eliminated entirely.
In the case of a Porsche engine there can be a piston oil squirter stuck open, or the pressure valve that routes oil to the squirters is stuck open and the squirters get oil all the time. This would I think show up as too low an oil pressure at hot idle.
Certainly excessive bearing clearances either the mains/rods (I think one might hear some knocking if the rod bearings that loose) and the cam shaft bearings.
Another source of a leak can be if the engine was apart that the assembly resulted in an oil leak -- some mating surfaces around oil galleys or oil supply holes were not properly treated to the sealant -- and there is an internal oil leak.
One has to be very careful about properly sealing one of these engines. The camshaft covers have oil holes from the base to the cover which feed the bearings and if the sealant leaks around one of these holes high pressure oil squirts out under the camshaft cover.
Unfortunately id'ing a squirter problem, or excessive clearances, or an internal oil leak is not easy without taking the engine apart and checking clearances and then ensuring during reassembly all oil passages/galleys and holes are properly sealed.
If the oil pump is "easy" to replace and this replaces just more than the gears but also the housing in which the gears run, it might be worth throwing a new pump at the low oil pressure problem. If you are sure there is truely a low oil pressure problem.
Oh, and don't resort to thicker oil. I won't help. I have run both 0w-40 and 5w-50 (not a typo for 15w-50) in both of my cars and I can't tell which oil is in the engine by the Turbo's oil pressure gage or by any other method other than looking at the label of the bottles of oil I used or what the tech wrote on the paperwork.
Where did you get the requirement of 5 bar at 5K rpm (I assume you are talking about an engine at operating temperature?)?? The Porsche manual specification is 3.5 (or above) bar at 5K rpm. I am not sure why you are trying to hit that spec of 5bar at 5k??
I am taking my Indy's word that spec is 5bar at 5K. If that's not the case - and if you can post anything to the contrary - man, I'd be so appreciative. It would set my mind at ease a bit.
Out next step is to source an oil pump rebuild kit - or a whole new oil pump.
I will continue to update this. Right now - the availability of parts for the oil pump rebuild is the main issue. (In the meantime - I am taking my 997 to the track this weekend to work out some frustrations).
He is saying you are over thinking this.......... I have owned 2 P cars since '92, still have them both. oil P at idle is near 1 bar on both of them....... depending on oil, a tad + or a tad -. 3.5 bar is plenty no matter the rpm.
I got a bit of paranoia after reading this thread as I get almost 4.5 bar at 5k but I've looked at a few YouTube vids of people filming acceleration in there 996's and it gives a good indication on engine temp rpm and oil pressure and most seem to only go up to same as mine max, I think lower mileage engines tend to have more hot idle pressure , I get 1.25 bar at normal hot idle, it drops to a bar if I'm in traffic and she starts getting to the point where the second stage fans are coming in, I'm running the millers 10w50 nanodrive hartech recommends and it seems better than the castrol 5w40 I ran previously, hot idle had improved but it doesn't take much revs for it to go up , by 3k it's at the 3.5 bar stated in the Porsche manual.
Oh no! You have to drain that Mork's nano-nano stuff out right now, oil from *Ork is not Porsche approved,
replace it with Joe Gibbs racing oil per LN Engineering. Which as far as I know isn't Porsche approved either.
You Tube
*
https://www.google.com/search?q=mork...obile&ie=UTF-8
